From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <dc783463b845c1e7832fa5cacf19b73a@quanstro.net>
To: 9fans@9fans.net
From: erik quanstrom <quanstro@quanstro.net>
Date: Tue, 22 Jul 2008 14:19:49 -0400
In-Reply-To: <0b6ee1c89e58c4e41f8810c5ba0c1cae@quanstro.net>
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Subject: Re: [9fans] Building new kernel.
Topicbox-Message-UUID: ed7fd96e-ead3-11e9-9d60-3106f5b1d025

> this would be expected due to the pull which sets the mtimes of
> new files to be older than the .8s.  try "mk clean" before proceeding.

i should explain that type signatures are 32-bit
signatures in .$O files that define the type of
external symbols.  the c compiler sets the type
signature to zero unless the -T flag is given.
if both signatures are not zero, the linker
checks to see that they match.

thus if you try to link a.c with decl
	extern int fu;
with b.c
	long fu
it will work perfectly if the -T flag is not
given (since there is a deep assumption
in plan 9 that int == long).  but i the
-T flag is given, it will fail with a type
signature error.

- erik

----
	minooka; cat a.c
	long fu;
	minooka; cat b.c
	#include <u.h>
	#include <libc.h>

	extern int fu;

	void
	main(void)
	{
		print("%d\n", fu);
	}

	minooka; 8c a.c && 8c b.c && 8l a.8 b.8 && 8.out
	0

	minooka; 8c -T a.c && 8c b.c && 8l a.8 b.8 && 8.out
	0

	minooka; 8c a.c && 8c -T b.c && 8l a.8 b.8 && 8.out
	0

	minooka; 8c -T a.c && 8c -T b.c && 8l a.8 b.8 && 8.out
	main: incompatible type signatures 5ef20f47(a.8) and 4151d5bd(b.8) for fu